The Session Initiation Protocol (SIP), together with extensions defined by the SIP Instant Messaging and Presence Leveraging Extensions (SIMPLE), provides for the implementation of presence servers which receive and maintain presence information regarding entities called “presentities,” such as computer or cell phone users, and provide presence information to subscribers who request presentity presence information.
Extensions to SIP/SIMPLE have been proposed for accommodating group presentities, such as a “customer service” presentity whose presence information includes the names and email addresses of currently-available customer service representatives. However, such extensions require that the group presence information be maintained using an external application. For example, where an ad-hoc group is formed, such as for a conference call that is managed by a conference server, and a group presentity for the conference is created on a presence server, the comings and goings of group participants to and from the conference call currently requires each participant to separately update both the conference server as well as the presence server. A mechanism for managing ad-hoc group presence information that reduces participant-side management responsibility would therefore be desirable.